Grain-based desserts and pizza as well as soda, sports drinks and energy drinks make up the top sources of calories for kids age 2 to 18, according to the publication "Dietary Guidelines for Americans, 2010." With those stats, it's not so surprising that the obesity rate in children has risen from between 4 percent and 6 percent, depending on age range, in the early 1970s to between 10 percent and 20 percent by 2008. A diet laden with junk food not only affects weight but other facets of a child's life, too.